This invention relates to textile machinery, such as tufting machines and the like, and is particularly directed to yarn feed roller pattern attachments therefor.
Wide use is being made of yarn feed roller pattern attachments for producing variations in pile height in pile fabrics such as carpeting. Representative of such feed roller pattern attachments are those disclosed in the following U.S. Pat. Nos. Card, No. 2,862,465; Nix, No. 2,875,714; Card, No. 2,966,866; MacCaffray, No. 3,001,388; Card, No. 3,075,482; Hammel, No. 3,103,187; Beasley, No. 3,134,529; Erwin, et al, No. 3,272,163; Singleton, No. 3,489,326; Short, No. 3,605,660; Short, No. 3,752,094; Hammel, No. 3,847,098; Lear et al, No. 3,926,132 and Prichard et al, No. 3,955,514. These attachments include a plurality of yarn feed rollers which feed yarn to the needles of the tufting machine. Each of the feed rollers is selectively driven at one of a plurality of different speeds independently of the other feed rolls by means of clutches controlled by a pattern control. The amount of yarn supplied to the needles of a tufting machine is determined by the rotational speed of the feed rollers about which the yarn is wound, so that with a fixed needle stroke the amount of yarn supplied to the needle determines the pile height of the fabric produced. To create patterned pile effects the amount of yarn fed to the individual needles may be varied by driving the feed rollers selectively at the different speeds.
Since each needle receiving yarn from a given roller must necessarily always produce a pile loop as the same height as that of the other needles receiving yarn from that roller, the number of pattern repeats across the width of the work product is limited by the number of needles receiving yarn from each roller. Thus, the limitations on the number of rollers restricts the carpet designer to designs which repeat frequently across the width of the carpet. It is therefore desirable to have a pattern attachment capable of individual yarn end control or at least approaching such control. Due to space limitations the prior art designs have not generally been adoptable to the large number of rollers required for individual yarn end control. The Short patents and the Prichard et al patent are attempts toward this end, however these necessitate complicated drive constructions.
The most successful prior art feed roller attachments have been those, such as illustrated in the aforesaid Singleton, Hammel No. 3,847,098 and Lear et al patents, in which the rollers are journalled on driven shafts and electromagnetic clutch elements are mounted within the rollers for drivingly transmitting the rotation of the shaft to the rollers selectively. However, because the electromagnetic clutches include electrical coils and other wiring within the rollers, the rollers are relatively wide and limits the number of rollers that can be utilized. Moreover, since these feed roller attachments comprise a large number of such clutches, and since certain of the clutch elements have a relatively short life, frequent servicing of the roller units has been occassioned.